Faunal assemblages of benthic megainvertebrates inhabiting sea scallop grounds from eastern Georges Bank, in relation to environmental factors

Abstract

A total of 140 species of megainvertebrates representing ten phyla were identified, from which epibenthic taxa accounted for c76%. Molluscs, crustaceans, annelids and echinoderms were best represented, with bivalves ranking first in abundance (55%) and biomass (86%). Significant changes of species diversity, total abundance, and total biomass were found according to sediment type, but not according to depth (except for total biomass). No clear bathymetric pattern was observed, although the mean number of species, mean total density (<80m), and mean total biomass (<60m) decreased with increasing depth in the deepest zone. Maximum megafaunal richness was found in biogenic bottoms; minimum value occurred in sand dunes. Three bivalve species (Spisula solidissima, Arctica islandica, Placopecten magellanicus) made up to 71% of total biomass overall, while 14 species (predominantly Anomia spp. Arctica islandica and Ophiopholis aculeata) accounted for 70% of total density. Six megafaunal associations related to two major assemblages (biogenic sand-gravel and sand-shell fauna) were defined from multivariate analyses. Sediment type, tidal current speed, turbulent mixing, and food availability appear to be the major distribution-regulating factors of the megabenthos in the 55-105m depth range. Density-dependent predator-prey relationships were the main biological associations shown. -from Authors